Yes the Americans have a name for it and are experts at it, it's called capitalism.
Don't forget that Amazon, among others, also sells on eBay and also buys from merchants who deliver direct to you with Amazon adding its mark up on what you pay. Same as the eBay sellers.
Stopped shopping via eBay long time ago.
Not rocket science, shop around. Caveat Emptor.
As said, Not only are fools separated from their money but more money than brains comes to mind.
One of my other hobbies is collecting money, not having a great deal of success but I keep working at it